The zygoma is a bone that provides vital contributions to both the structure and aesthetic of the midface and articulates with several bones of the craniofacial skeleton. The zygoma and its articulations comprise the zygomaticomaxillary complex (ZMC). Fractures of the zygomatic arch (ZA) or any of its bony articulations can cause significant functional and cosmetic morbidity. The management of the zygomatic arch and ZMC fractures should be patient-specific but range from simple observation to open reduction with internal fixation (ORIF).
The zygoma is the most anterolateral projection of the midface. It plays a key role structurally as it absorbs and dissipates forces away from the cranial base. The zygoma also comprises a significant portion of the inferior and lateral orbital walls; thus, fracture of the zygoma warrant investigation into fractures of the orbit.
The zygoma has four articulations, referred to as the ZMC complex:
NOTE: Fractures of the ZMC complex may be mistakenly referred to as "tripod fractured," though the correct terminology is, in fact, "tetrapod fracture," given the four articulations of the zygoma as stated above.
Paresthesia of the face is a common sequela of a ZMC fracture given its proximity to sensory nerves such as the infraorbital nerve, the zygomaticofacial nerve, and the zygomaticotemporal nerve (all branches of cranial nerve V2).
Severe ZMC fractures may also result in an ipsilateral facial palsy since the facial nerve is intimately associated with the zygomatic arch. The facial nerve's frontal branch emerges from the parotid gland within the parotid-masseteric fascia and crosses superficial to the zygomatic arch in the innominate fascia deep to the superficial muscular aponeurotic system (SMAS). The frontal branch then transitions to the undersurface of the temporoparietal fascia where it travels to innervate the frontalis muscle.
The temporalis originates along the temporal line of the parietal and frontal bones and travels medially to the zygomatic arch to insert on the coronoid process of the mandible. It also has attachments to the zygoma.
The masseter originates on the inferior aspect of the zygoma and zygomatic arch and inserts on the angle of the mandible.
The zygomaticus major and minor are muscles of facial expression that originate on the zygoma and insert near the corner of the mouth to assist with commissure elevation.
Tubercle of Whitnall: The attachment site of the lateral canthal tendon located on the medial surface of the frontal process of the zygoma.
Fractures of the zygoma are almost always the result of high impact trauma. The most common mechanisms are assault, motor vehicle collisions, falls, and sporting injuries.
Most zygomatic fractures occur in men between the ages of 20 and 29. ZMC fractures are common, as estimates suggest that ZMC fractures comprise 25% of facial fractures.
It is crucial to ascertain the mechanism and timing of the injury. Note whether the injury was caused by blunt or penetrating trauma, as penetrating trauma is more likely to involve deeper-lying neurovascular structures. One should ask about prior facial trauma or facial surgeries, which may make fracture repair more difficult.
As with any trauma patient, it is important to start the examination with an evaluation of the "ABCs." Ensure the patient has an adequate airway, is breathing spontaneously, and that any bleeding is under control. It is also vitally important to "clear" the cervical spine for any associated injury. Inspect the face, noting any obvious asymmetry, lacerations, and ecchymosis of skin. Ipsilateral epistaxis is common and requires controlling if severe. An ophthalmologic exam should be performed, including visual acuity, visual fields, and extraocular movements. In a patient with a ZMC injury, the facial flattening may be apparent from a birds-eye view, which is caused by depression of the malar eminence; however, the facial flattening may get obscured by overlying soft tissue edema. The clinician should note the position of the globe. Enophthalmos may be visible from a worms-eye view. The face should be palpated, noting any bony step offs or mobility of the underlying craniofacial skeleton. A comprehensive cranial nerve examination should be completed, paying special attention to facial movement and sensation.
After a comprehensive history and physical examination, imaging is almost always necessary if a zygomatic arch or ZMC fracture is suspected. Historically, the Waters view plain film was used to evaluate ZMC fractures. A computed tomography (CT) scan is now the gold standard imaging modality. The 3-dimensional reconstruction is particularly useful for preoperative planning. There may also be a role for the intraoperative use of CT to assess the adequacy of fracture reduction, but there is no strong evidence to support the routine use of this practice.
Classification of ZMC Fractures
Various classification systems have been used to categorize ZMC fractures further. Below is a widely used system proposed by Zingg:
Management of ZMC fractures can broadly classify into three categories: medical management, closed reduction, and open reduction with internal fixation (ORIF). Management of ZMC fractures is controversial and requires tailoring to each case.
Zygomatic fractures are usually observable if there is minimal or no displacement of fracture segments. Additionally, medical management may be the choice if other comorbidities preclude safe surgery. No strong evidence supports the use of prophylactic antibiotics in upper and midface fractures, though some surgeons prescribe a 5 to 7-day course of antibiotics, particularly if a communication exists with the maxillary sinus. If prescribed, antibiotics should cover sinonasal flora.
The indications for operative management of zygomatic arch and ZMC fractures are to restore the form and function of the ZMC. Fractures of the ZMC or zygomatic arch can often lead to unsightly malar depression, which should be corrected to restore a normal facial contour. ZMC fractures can also cause significant functional issues, including trismus, enophthalmos and/or diplopia, and paresthesias of the infraorbital nerve. A suspected globe injury is a contraindication to operative management of ZMC fractures and should be diagnosed/addressed before any surgical intervention to repair the zygomatic arch or ZMC fracture sites.
A principle of facial fracture repair includes the ability to reduce and/or fixate fractures that involve the facial buttresses to restore the structural integrity of the midface. Several methods exist to repair zygomatic arch and ZMA fractures, though closed reduction may be adequate for simple, low-velocity injuries of the zygomatic arch (see TYPE A1 below) that are non-displaced or minimally displaced and remain stable after initial attempts of reduction. ORIF should be the choice for fractures that are comminuted or are likely to be unstable after reduction. Typically, profile titanium mini-plates are commonly used to fixate the fracture sites, working in a manner to repair fractures from laterally to medially and from stable to non-stable segments. Absorbable plates may also be used for fixation in cases where follow-up is unlikely, but such plates should not be routinely used as absorbable plates are structurally weaker in biomechanical studies.
Herein we summarize a management algorithm based on Zingg's classification system of ZMC fractures as described above (see EVALUATION) :
Orbital floor exploration and repair
Indications for the repair of the orbital floor are controversial. Generally, if greater than 50% of the floor is involved or the defect is 1 to 2 cm^2 or larger, the orbital floor should be repaired. Additional indications include a non-resolving oculocardiac reflex, primary diplopia, enophthalmos, and entrapment of extraocular muscles. Many different materials can be used, including titanium mesh, dura, temporalis fascia, and other allogeneic implants. After repair, a forced duction test should be performed to ensure normal mobility of the globe.
Number of fixation points
There is no consensus as to how many fixation points are necessary when treating ZMC fractures. In general, the more comminuted or unstable a fracture is, the more fixation points will be needed to ensure a good result. A recent meta-analysis suggested that three-point fixation had less fracture instability and orbital dystopia at three months post-operatively as compared to two-point fixation, but the quality of evidence was low. An intraoperative CT scan is used to visualize the articulations of the zygoma and verify adequate reduction. The zygoma and its articulations can also be palpated after fixation to determine if additional fixation points are needed.
Order of plating
There is no universal order of plating in multipoint fixation. In single-point fixation, the ZM buttress usually gets plated. The zygomaticofrontal suture can also get plated, though most would argue that the intraoral incision used to plate the ZM buttress is less morbid than approaches to the ZF suture. In two-point fixation, the zygomaticofrontal suture should be plated first, followed by the ZM buttress. In three or four-point fixation, the ZF requires plating first, then the ZM buttress, then the IOR followed by the zygomatic arch if necessary. If one plans to plate the zygomatic arch from the outset, it can often be plated first to ensure adequate projection of the ZMC. If concomitant repair of the orbital floor is necessary, it should take place after the zygoma has had a reduction performed.
Soft tissue suspension
If the lateral canthal tendon has suffered disruption, it requires resuspension with suturing to the tubercle of Whitnall. The malar eminence can be suspended to prevent ectropion or scleral show.
Summary of Surgical Approaches
Timing of repair
Fracture repair should take place as quickly as possible before scarring, and healing of bony fragments begins. Because significant facial edema guises aesthetic deformities and increases exposure difficulty, fracture repair should ideally take place within 7 to 10 days of the initial injury. Fracture repair from 2 to-6 weeks post-injury is possible, but usually more difficult due to ensuing fibrosis and scarring. Fracture repair past six weeks is extremely challenging, but the surgeon can facilitate it by the use of intraoperative imaging and navigation. If orbital floor repair is necessary, it should ideally occur within two weeks of the injury.
As stated above, the zygoma comprises a significant portion of the inferior and lateral orbital walls; thus, any fracture of the zygoma warrant investigation into fractures or injury of the orbit. Also, cervical spine injury must be ruled out, as well as other concomitant facial fractures, including frontal sinus, nasal, midface (e.g., Lefort, NOE), and mandible fractures. Septal hematoma should be ruled out as well to avoid septal necrosis and resultant saddle nose deformity. Lastly, malocclusion requires attention, as well.
Comminuted fractures of the ZMC have worse outcomes than non-comminuted fractures and have a higher rate of reoperation. Estimates are that up to 5% of patients will require a second operation within four weeks due to inadequate fracture reduction. Patients may have persistent paresthesia, enophthalmos, diplopia, and temporomandibular joint dysfunction. Research estimates that some degree postoperative asymmetry occurs in 20 to 40% of patients, with major asymmetry occurring in 3 to 4% of patients. Permanent paresthesia occurs in 22 to 65% of patients.
Complications from ZMC fractures can be related to the initial injury itself or operative management.
Orbital complication (usually related to clinically significant concomitant orbital floor fracture):
Postoperative care and recovery vary depending on the degree of injury and subsequent repair methods involved. Regardless, the patient should be advised to refrain from strenuous activity for at least two weeks to allow for complete healing with minimal bruising and swelling. Depending on the fractures involved, ancillary care postoperatively may include lubricating eye drops (orbital fractures), nasal irrigations (communication with the sinonasal contents), oral rinses (intraoral incisions used), or soft diet (mandible fractures/malocclusion). Incision lines require antibiotic ointment application (must be an ophthalmic ointment for periorbital incisions) for at least 72 hours postoperatively and then transitioned to petroleum ointment thereafter until the incisions heal completely. Avoidance of sun exposure and/or proper sun protection, as well as the use of silicone-based scar creams/ointments, may help improve the appearance of any scars. The patient should be followed closely postoperatively for any potential complications, namely related to infection and/or visual complaints. Visits usually occur at one-week post-operatively and then a few weeks thereafter up until the fractures appear stable and any complications are ruled out.
As stated previously, a full trauma workup should be administered to rule out any concomitant injuries to determine the most appropriate consultations (e.g., neurosurgery, ophthalmology, orthopedic surgery, plastic surgery, otolaryngology, oral-maxillofacial surgery, vascular surgery, etc.).
NOTE: Ocular injuries occur in 20 to 60% of ZMC fractures. There should be a very low threshold for ophthalmology consultation if an orbital injury is suspected.
It is important to thoroughly counsel patients regarding the potential acute and long term complications of surgery so that they can make an informed treatment decision.
Successful management of zygomatic arch and ZMC fractures requires coordination between the surgical team (otolaryngology, plastic surgery, oral and maxillofacial surgery), ophthalmology, anesthesiology, trauma surgery, and perioperative nursing, operating as a cohesive, interprofessional team. A careful preoperative evaluation is paramount. It is essential to identify and document concomitant injuries to ensure that the most pressing issues get addressed first — any ocular injury requires attention before fracture management. Comorbidities require consideration when deciding on operative versus conservative management. Postoperatively, the specialty trained nursing staff should carefully monitor visual acuity and extraocular movements. The patient should understand that paresthesia of the infraorbital nerve and trismus are not uncommon and may persist. The surgical team and nursing staff should caution the patient to abstain from heavy lifting and strenuous activity for at least two weeks after surgery. This interprofessional team approach is the best means by which to attain positive patient outcomes with minimal adverse events. [Level 5]
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